With the popularization of the mobile internet and the smart phone, requirements for the mobile data traffic are growing fast. In the next decade (2011-2020), the mobile data traffic will double every year, and will be increased by a thousand times in ten years.
The increase of the percentage of the data service in the operators' networks affects the conventional carrier-grade service. However, the earnings growth of the data service is not proportional to the traffic load, since the data service is billed on the data traffic. In addition, the fast-growing data service poses severe challenges to the transmission capacity of the mobile network. Most of mobile data services mainly occur indoor and in hotspots environment, which is embodied as nomadism/local wireless access scenes. According to statistics, almost 70% of the present mobile data services occur indoor, and the percentage will be growing continuously and will exceed 80% by 2012. Therefore, the solution to the high-speed data service for the indoor coverage and hotspot coverage is imperative to the operator.
As to the data service for the indoor coverage and hotspot coverage, its features are: on one side, the users are generally fixed users or users moving in low speed; the user have no high requirement of mobility, thereby having the feature that the wireless channel has small delay spread and the circumstance of the wireless channel changes slowly; on the other side, the data service is mainly the internet service based on the IP (Internet Protocol), and the requirements thereof to QoS are relatively simple and are far below the carrier-grade service's requirements. After the LTE/LTE-Advanced technology is introduced, the LTE/LTE-Advanced system is mainly applied to the circumstances with large coverage area (500-1000 kilometers) and various channels (with a rate from 3 kilometers per hour to 350 kilometers per hour, and a channel delay from less than one microsecond to less than twenty microseconds) and is not suitable for the application circumstance of the conventional the data service for the indoor coverage and hotspot coverage. Thus, when the LTE/LTE-Advanced system carries IP data package service with massive data flow and low rate, the use of the conventional solution to pilot transmission for the data service for the indoor coverage and hotspot coverage will cause problems such as too much pilot overhead, low efficiency and high cost. In the conventional solution to pilot transmission for the data service for the indoor coverage and hotspot coverage, each uplink/downlink subframe transmits the demodulation pilot, which certainly will cause problems such as too much pilot overhead, low efficiency and high cost. Therefore, when applying the LTE/LTE-Advanced technology to such channel circumstances as indoor and hotspots coverage with high rate, it is necessary and urgent to reduce the pilot overhead and improve system capacity to avoid the above problems.